1. Field of the Invention
The present invention relates generally to microphones and, more particularly, to "lapel" or "lavalier" microphones.
2. Description of Related Art
Microphones are electronic devices commonly used in the amplification and/or recording of sounds. Generally, a microphone comprises a microphone casing and a transducer. The microphone casing has an aperture for receiving sound vibrations. The transducer, which is used to convert the sound vibrations into electrical signals, is disposed within the casing near the aperture. In use, sound vibrations enter the microphone through the aperture and impinge on the transducer. The transducer then converts these sound vibrations into electrical signals, which are then transmitted to an amplifier for amplification. Typically, the amplifier is disposed at a remote location, and consequently, a microphone cable is used to transmit the signals from the microphone to the amplifier. After being amplified, the electrical signals are then transmitted either to a receiver, where the signals are converted back into audible sound, or to a recording device, where the signals are recorded on magnetic tape or other similar material.
Although they are indispensable to film and television-making, microphones are considered by most to be aesthetically displeasing. Consequently, considerable effort has been expended to find ways to make microphones less conspicuous to audiences without sacrificing the sensitivity of the microphones. One approach has been to hide or to camouflage the microphones so that they will not be seen by audiences but will still pick up the desired sounds. Another approach has been to have one or more of the actors wear a very small microphone, often called a "lapel" or "lavalier" microphone, on or under his clothing. Unfortunately, however, lavalier microphones create an entirely new problem, namely, interference. Microphone interference may be defined as that portion of sound output that is undesired. In general terms, it is sound picked up by the microphone and transmitted to the audience that is different from sound that would be heard by a person not hearing the sound through a microphone. Interference most common to lavalier microphones is caused either by the rustling of clothing in the immediate vicinity of the microphone or by direct physical contact with the microphone itself. It should be noted that these two forms of interference are in fact different. To illustrate this point, one may perform the following experiment.
First, the finger and thumb of one hand are rubbed together lightly near the waist. The sound produced by the rubbing is barely perceptible. If, however, the finger and thumb are rubbed together near the aural canal of the ear, the rubbing produces a loud scratching noise. Now, if the other hand is used to block the aural canal while the rubbing takes place, the sound again becomes imperceptible. However, if instead of rubbing together the finger and thumb, the finger is rubbed along the outer ear while the aural canal is closed, a loud scraping noise is again heard.
In the above-described experiment, the noise heard from rubbing together the finger and thumb near the aural canal is analogous to the interference produced by rubbing clothing together near the microphone. For purposes of this application, this type of interference will be referred to as "ambient interference." The noise heard from rubbing the finger along the outer ear while the aural canal is closed is analogous to the interference caused by physical contact with the microphone itself. For purposes of this specification and claims, this type of interference will be referred to as "mechanical interference."
In U.S. Pat. No. 3,651,286, issued to Gorike et al., there is disclosed a lavaliar microphone assembly designed to protect against frictional noises. The microphone assembly comprises a longitudinally elongated microphone capsule and a tubular casing, the capsule being fixedly mounted and supported within the casing at least at each end by an axially spaced resilient vibration absorbing member. The purpose of the absorbing members is to shield the microphone capsule from noise transmitted to the casing.
While the above-described Gorike assembly appears to address the problem of mechanical interference caused by contact with the microphone capsule, it does not address the problem of ambient interference, which is caused, for example, by the rubbing together of clothes in the vicinity of the microphone.
Other references of interest include U.S. Pat. No. 2,327,320, issued to H. B. Shapiro; U.S. Pat. No. 2,336,828, issued to W. A. Zarth; U.S. Pat. No. 2,351,400, issued to R. W. Carlisle; U.S. Pat. No. 2,505,551, issued to H. S. Knowles; U.S. Pat. No. 2,673,898, issued to P. Reichert.